[RFC] genalloc:add an gen_pool_alloc_align func to genalloc

Bytes alignment is required to manage some special ram,
so add gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with
align = 1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc directory,
using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory,
Scott wood hopes to use genalloc to manage the muram, after discussing 
with scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

 include/linux/genalloc.h | 10 +++++++---
 lib/genalloc.c           | 38 ++++++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 1ccaab4..65fdf14 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h

@@ -96,6 +96,8 @@ static inline int gen_pool_add(struct gen_pool *pool, unsigned long addr,
 }
 extern void gen_pool_destroy(struct gen_pool *);
 extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
+extern unsigned long gen_pool_alloc_align(struct gen_pool *, size_t,
+		unsigned long align);
 extern void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size,
 		dma_addr_t *dma);
 extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);

@@ -108,14 +110,16 @@ extern void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo,
 		void *data);
 
 extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);
 
 extern unsigned long gen_pool_first_fit_order_align(unsigned long *map,
 		unsigned long size, unsigned long start, unsigned int nr,
-		void *data);
+		void *data, unsigned long align_mask);
 
 extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);
 
 extern struct gen_pool *devm_gen_pool_create(struct device *dev,
 		int min_alloc_order, int nid);

diff --git a/lib/genalloc.c b/lib/genalloc.c
index d214866..dd63448 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c

@@ -258,19 +258,22 @@ void gen_pool_destroy(struct gen_pool *pool)
 EXPORT_SYMBOL(gen_pool_destroy);
 
 /**
- * gen_pool_alloc - allocate special memory from the pool
+ * gen_pool_alloc_align - allocate special memory from the pool
  * @pool: pool to allocate from
  * @size: number of bytes to allocate from the pool
+ * @align: number of bytes to align
  *
  * Allocate the requested number of bytes from the specified pool.
  * Uses the pool allocation function (with first-fit algorithm by default).
  * Can not be used in NMI handler on architectures without
  * NMI-safe cmpxchg implementation.
  */
-unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+unsigned long gen_pool_alloc_align(struct gen_pool *pool, size_t size,
+		unsigned long align)
 {
 	struct gen_pool_chunk *chunk;
 	unsigned long addr = 0;
+	unsigned long align_mask;
 	int order = pool->min_alloc_order;
 	int nbits, start_bit = 0, end_bit, remain;
 

@@ -281,6 +284,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 	if (size == 0)
 		return 0;
 
+	align_mask = ((align + (1UL << order) - 1) >> order) - 1;
 	nbits = (size + (1UL << order) - 1) >> order;
 	rcu_read_lock();
 	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {

@@ -290,7 +294,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 		end_bit = chunk_size(chunk) >> order;
 retry:
 		start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
-				pool->data);
+				pool->data, align_mask);
 		if (start_bit >= end_bit)
 			continue;
 		remain = bitmap_set_ll(chunk->bits, start_bit, nbits);

@@ -309,6 +313,22 @@ retry:
 	rcu_read_unlock();
 	return addr;
 }
+EXPORT_SYMBOL(gen_pool_alloc_align);
+
+/**
+ * gen_pool_alloc - allocate special memory from the pool
+ * @pool: pool to allocate from
+ * @size: number of bytes to allocate from the pool
+ *
+ * Allocate the requested number of bytes from the specified pool.
+ * Uses the pool allocation function (with first-fit algorithm by default).
+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
+ */
+unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+{
+	return gen_pool_alloc_align(pool, size, 1);
+}
 EXPORT_SYMBOL(gen_pool_alloc);
 
 /**

@@ -502,9 +522,10 @@ EXPORT_SYMBOL(gen_pool_set_algo);
  * @data: additional data - unused
  */
 unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
-		unsigned long start, unsigned int nr, void *data)
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask)
 {
-	return bitmap_find_next_zero_area(map, size, start, nr, 0);
+	return bitmap_find_next_zero_area(map, size, start, nr, align_mask);
 }
 EXPORT_SYMBOL(gen_pool_first_fit);
 

@@ -520,7 +541,7 @@ EXPORT_SYMBOL(gen_pool_first_fit);
  */
 unsigned long gen_pool_first_fit_order_align(unsigned long *map,
 		unsigned long size, unsigned long start,
-		unsigned int nr, void *data)
+		unsigned int nr, void *data, unsigned long align_mask)
 {
 	unsigned long align_mask = roundup_pow_of_two(nr) - 1;
 

@@ -541,13 +562,14 @@ EXPORT_SYMBOL(gen_pool_first_fit_order_align);
  * which we can allocate the memory.
  */
 unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
-		unsigned long start, unsigned int nr, void *data)
+				unsigned long start, unsigned int nr,
+				void *data, unsigned long align_mask)
 {
 	unsigned long start_bit = size;
 	unsigned long len = size + 1;
 	unsigned long index;
 
-	index = bitmap_find_next_zero_area(map, size, start, nr, 0);
+	index = bitmap_find_next_zero_area(map, size, start, nr, align_mask);
 
 	while (index < size) {
 		int next_bit = find_next_bit(map, size, index + nr);

-- 
2.1.0.27.g96db324

On 07/09/2015 12:47 AM, Zhao Qiang wrote:

Bytes alignment is required to manage some special ram,
so add gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with
align = 1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc directory,
using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory,
Scott wood hopes to use genalloc to manage the muram, after discussing
with scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

gen_pool supports custom allocation algorithms. I thought this was discussed
previously and the conclusion was that if you wanted alignment you should
use custom allocation algorithms. I'm failing at finding any thread discussing
it though.

Perhaps another option would be to add another runtime argument to gen_pool
where you could pass the alignment to your custom allocation function. This
way alignment isn't inherently coded into any of the algorithms.

Passing 1 here would change the behavior of the existing algorithms which
were passing 0 for the align mask

Thanks,
Laura

On Thu, 2015-07-09 at 14:51 -0700, Laura Abbott wrote:

On 07/09/2015 12:47 AM, Zhao Qiang wrote:

quoted

Bytes alignment is required to manage some special ram,
so add gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with
align = 1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc 
directory,
using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory,
Scott wood hopes to use genalloc to manage the muram, after discussing
with scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

gen_pool supports custom allocation algorithms. I thought this was discussed
previously and the conclusion was that if you wanted alignment you should
use custom allocation algorithms. I'm failing at finding any thread 
discussing it though.

I hope that by "custom algorithm" you don't mean something implemented 
outside lib/genalloc.c, as this does not seem like such a specialized 
requirement that everyone must reimplement it separately.

Perhaps another option would be to add another runtime argument to gen_pool
where you could pass the alignment to your custom allocation function. This
way alignment isn't inherently coded into any of the algorithms.

That wouldn't let the alignment change for each allocation (and could already 
be done with pool->data).  I suppose one could call get_pool_set_algo() with 
different data (or modify the memory that pool->data is already pointing to) 
before each allocation, but that's a bit clunky...  If making alignment part 
of the mainstream flow is undesired for some reason, how about a 
gen_pool_alloc_data() that lets it be passed in per-allocation (with 
gen_pool_alloc() being a wrapper that passes in pool->data)?

Yes, I know, we could do it in a wrapper (like cpm_muram_alloc() 
unnecessarily does), but why not make the interface better match the way it's 
used?

-Scott

On Thu, 2015-07-09 at 15:47 +0800, Zhao Qiang wrote:

What about the other call to bitmap_find_next_zero_area()?

-Scott

On 07/09/2015 03:17 PM, Scott Wood wrote:

On Thu, 2015-07-09 at 14:51 -0700, Laura Abbott wrote:

quoted

On 07/09/2015 12:47 AM, Zhao Qiang wrote:

quoted

Bytes alignment is required to manage some special ram,
so add gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with
align = 1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc
directory,
using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory,
Scott wood hopes to use genalloc to manage the muram, after discussing
with scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

gen_pool supports custom allocation algorithms. I thought this was discussed
previously and the conclusion was that if you wanted alignment you should
use custom allocation algorithms. I'm failing at finding any thread
discussing it though.

I hope that by "custom algorithm" you don't mean something implemented
outside lib/genalloc.c, as this does not seem like such a specialized
requirement that everyone must reimplement it separately.

If the functions are generic enough (which I think they are) they could stay
in genalloc.c as another option for people to use.

quoted

Perhaps another option would be to add another runtime argument to gen_pool
where you could pass the alignment to your custom allocation function. This
way alignment isn't inherently coded into any of the algorithms.

That wouldn't let the alignment change for each allocation (and could already
be done with pool->data).  I suppose one could call get_pool_set_algo() with
different data (or modify the memory that pool->data is already pointing to)
before each allocation, but that's a bit clunky...  If making alignment part
of the mainstream flow is undesired for some reason, how about a
gen_pool_alloc_data() that lets it be passed in per-allocation (with
gen_pool_alloc() being a wrapper that passes in pool->data)?

Yes, that's what I was thinking. I dropped the alloc from my 'runtime argument
to gen_pool_alloc' so it wasn't clear I was talking about allocation time and
not pool creation time.

Yes, I know, we could do it in a wrapper (like cpm_muram_alloc()
unnecessarily does), but why not make the interface better match the way it's
used?

Agreed.

-Scott

Thanks,
Laura

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-----Original Message-----
From: Laura Abbott [mailto:labbott@redhat.com]
Sent: Friday, July 10, 2015 5:51 AM
To: Zhao Qiang-B45475; lauraa@codeaurora.org
Cc: linux-kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
akpm@linux-foundation.org; olof@lixom.net; catalin.marinas@arm.com; Wood
Scott-B07421; Xie Xiaobo-R63061
Subject: Re: [RFC] genalloc:add an gen_pool_alloc_align func to genalloc
=20
On 07/09/2015 12:47 AM, Zhao Qiang wrote:

quoted

Bytes alignment is required to manage some special ram, so add
gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with align =3D
1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc
directory, using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory, Scott wood
hopes to use genalloc to manage the muram, after discussing with
scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

=20
gen_pool supports custom allocation algorithms. I thought this was
discussed previously and the conclusion was that if you wanted alignment
you should use custom allocation algorithms. I'm failing at finding any
thread discussing it though.
=20
Perhaps another option would be to add another runtime argument to
gen_pool where you could pass the alignment to your custom allocation
function. This way alignment isn't inherently coded into any of the
algorithms.
=20

quoted

  include/linux/genalloc.h | 10 +++++++---
  lib/genalloc.c           | 38 ++++++++++++++++++++++++++++++--------
  2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h index

1ccaab4..65fdf14 100644

--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h

@@ -96,6 +96,8 @@ static inline int gen_pool_add(struct gen_pool *pool,

unsigned long addr,

quoted

  }
  extern void gen_pool_destroy(struct gen_pool *);
  extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
+extern unsigned long gen_pool_alloc_align(struct gen_pool *, size_t,
+		unsigned long align);
  extern void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size,
  		dma_addr_t *dma);
  extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);

@@ -108,14 +110,16 @@ extern void gen_pool_set_algo(struct gen_pool

*pool, genpool_algo_t algo,

quoted

  		void *data);

  extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned

long size,

quoted

-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);

  extern unsigned long gen_pool_first_fit_order_align(unsigned long

*map,

quoted

  		unsigned long size, unsigned long start, unsigned int nr,
-		void *data);
+		void *data, unsigned long align_mask);

  extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned

long size,

quoted

-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);

  extern struct gen_pool *devm_gen_pool_create(struct device *dev,
  		int min_alloc_order, int nid);

diff --git a/lib/genalloc.c b/lib/genalloc.c index d214866..dd63448

100644

--- a/lib/genalloc.c
+++ b/lib/genalloc.c

@@ -258,19 +258,22 @@ void gen_pool_destroy(struct gen_pool *pool)
  EXPORT_SYMBOL(gen_pool_destroy);

  /**
- * gen_pool_alloc - allocate special memory from the pool
+ * gen_pool_alloc_align - allocate special memory from the pool
   * @pool: pool to allocate from
   * @size: number of bytes to allocate from the pool
+ * @align: number of bytes to align
   *
   * Allocate the requested number of bytes from the specified pool.
   * Uses the pool allocation function (with first-fit algorithm by

default).

quoted

   * Can not be used in NMI handler on architectures without
   * NMI-safe cmpxchg implementation.
   */
-unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+unsigned long gen_pool_alloc_align(struct gen_pool *pool, size_t size,
+		unsigned long align)
  {
  	struct gen_pool_chunk *chunk;
  	unsigned long addr =3D 0;
+	unsigned long align_mask;
  	int order =3D pool->min_alloc_order;
  	int nbits, start_bit =3D 0, end_bit, remain;

@@ -281,6 +284,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,

size_t size)

quoted

  	if (size =3D=3D 0)
  		return 0;

+	align_mask =3D ((align + (1UL << order) - 1) >> order) - 1;
  	nbits =3D (size + (1UL << order) - 1) >> order;
  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) { @@
-290,7 +294,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,

size_t size)

quoted

  		end_bit =3D chunk_size(chunk) >> order;
  retry:
  		start_bit =3D pool->algo(chunk->bits, end_bit, start_bit, nbits,
-				pool->data);
+				pool->data, align_mask);
  		if (start_bit >=3D end_bit)
  			continue;
  		remain =3D bitmap_set_ll(chunk->bits, start_bit, nbits); @@ -

309,6

quoted

+313,22 @@ retry:
  	rcu_read_unlock();
  	return addr;
  }
+EXPORT_SYMBOL(gen_pool_alloc_align);
+
+/**
+ * gen_pool_alloc - allocate special memory from the pool
+ * @pool: pool to allocate from
+ * @size: number of bytes to allocate from the pool
+ *
+ * Allocate the requested number of bytes from the specified pool.
+ * Uses the pool allocation function (with first-fit algorithm by

default).

quoted

+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
+ */
+unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size) {
+	return gen_pool_alloc_align(pool, size, 1);

=20
Passing 1 here would change the behavior of the existing algorithms which
were passing 0 for the align mask

When passing 1 here(align_mask =3D ((align + (1UL << order) - 1) >> order) =
- 1), align_mask will be 0.
It will not change the behavior of the existing algorithms.

=20

quoted

+}
  EXPORT_SYMBOL(gen_pool_alloc);

  /**

@@ -502,9 +522,10 @@ EXPORT_SYMBOL(gen_pool_set_algo);
   * @data: additional data - unused
   */
  unsigned long gen_pool_first_fit(unsigned long *map, unsigned long

size,

quoted

-		unsigned long start, unsigned int nr, void *data)
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask)
  {
-	return bitmap_find_next_zero_area(map, size, start, nr, 0);
+	return bitmap_find_next_zero_area(map, size, start, nr, align_mask);
  }
  EXPORT_SYMBOL(gen_pool_first_fit);

@@ -520,7 +541,7 @@ EXPORT_SYMBOL(gen_pool_first_fit);
   */
  unsigned long gen_pool_first_fit_order_align(unsigned long *map,
  		unsigned long size, unsigned long start,
-		unsigned int nr, void *data)
+		unsigned int nr, void *data, unsigned long align_mask)
  {
  	unsigned long align_mask =3D roundup_pow_of_two(nr) - 1;

@@ -541,13 +562,14 @@ EXPORT_SYMBOL(gen_pool_first_fit_order_align);
   * which we can allocate the memory.
   */
  unsigned long gen_pool_best_fit(unsigned long *map, unsigned long

size,

quoted

-		unsigned long start, unsigned int nr, void *data)
+				unsigned long start, unsigned int nr,
+				void *data, unsigned long align_mask)
  {
  	unsigned long start_bit =3D size;
  	unsigned long len =3D size + 1;
  	unsigned long index;

-	index =3D bitmap_find_next_zero_area(map, size, start, nr, 0);
+	index =3D bitmap_find_next_zero_area(map, size, start, nr,
+align_mask);

  	while (index < size) {
  		int next_bit =3D find_next_bit(map, size, index + nr);

=20
Thanks,
Laura

On 07/12/2015 07:22 PM, Zhao Qiang wrote:

quoted

-----Original Message-----
From: Laura Abbott [mailto:labbott@redhat.com]
Sent: Friday, July 10, 2015 5:51 AM
To: Zhao Qiang-B45475; lauraa@codeaurora.org
Cc: linux-kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
akpm@linux-foundation.org; olof@lixom.net; catalin.marinas@arm.com; Wood
Scott-B07421; Xie Xiaobo-R63061
Subject: Re: [RFC] genalloc:add an gen_pool_alloc_align func to genalloc

On 07/09/2015 12:47 AM, Zhao Qiang wrote:

quoted

Bytes alignment is required to manage some special ram, so add
gen_pool_alloc_align func to genalloc.
rename gen_pool_alloc to gen_pool_alloc_align with a align parameter,
then provide gen_pool_alloc to call gen_pool_alloc_align with align =
1 Byte.

Signed-off-by: Zhao Qiang <redacted>
---
FSL's IP block QE require this function to manage muram.
QE supported only PowerPC, and its code was put under arch/powerpc
directory, using arch/powerpc/lib/rheap.c to manage muram.
Now it support both arm(ls1021,ls1043,ls2085 and such on) and powerpc,
the code need to move from arch/powerpc to public direcory, Scott wood
hopes to use genalloc to manage the muram, after discussing with
scott, we decide to add gen_pool_alloc_align to meet the requirement
for bytes-alignment.

gen_pool supports custom allocation algorithms. I thought this was
discussed previously and the conclusion was that if you wanted alignment
you should use custom allocation algorithms. I'm failing at finding any
thread discussing it though.

Perhaps another option would be to add another runtime argument to
gen_pool where you could pass the alignment to your custom allocation
function. This way alignment isn't inherently coded into any of the
algorithms.

quoted

   include/linux/genalloc.h | 10 +++++++---
   lib/genalloc.c           | 38 ++++++++++++++++++++++++++++++--------
   2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h index

1ccaab4..65fdf14 100644

--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h

@@ -96,6 +96,8 @@ static inline int gen_pool_add(struct gen_pool *pool,

unsigned long addr,

quoted

   }
   extern void gen_pool_destroy(struct gen_pool *);
   extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
+extern unsigned long gen_pool_alloc_align(struct gen_pool *, size_t,
+		unsigned long align);
   extern void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size,
   		dma_addr_t *dma);
   extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);

@@ -108,14 +110,16 @@ extern void gen_pool_set_algo(struct gen_pool

*pool, genpool_algo_t algo,

quoted

   		void *data);

   extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned

long size,

quoted

-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);

   extern unsigned long gen_pool_first_fit_order_align(unsigned long

*map,

quoted

   		unsigned long size, unsigned long start, unsigned int nr,
-		void *data);
+		void *data, unsigned long align_mask);

   extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned

long size,

quoted

-		unsigned long start, unsigned int nr, void *data);
+		unsigned long start, unsigned int nr, void *data,
+		unsigned long align_mask);

   extern struct gen_pool *devm_gen_pool_create(struct device *dev,
   		int min_alloc_order, int nid);

diff --git a/lib/genalloc.c b/lib/genalloc.c index d214866..dd63448

100644

--- a/lib/genalloc.c
+++ b/lib/genalloc.c

@@ -258,19 +258,22 @@ void gen_pool_destroy(struct gen_pool *pool)
   EXPORT_SYMBOL(gen_pool_destroy);

   /**
- * gen_pool_alloc - allocate special memory from the pool
+ * gen_pool_alloc_align - allocate special memory from the pool
    * @pool: pool to allocate from
    * @size: number of bytes to allocate from the pool
+ * @align: number of bytes to align
    *
    * Allocate the requested number of bytes from the specified pool.
    * Uses the pool allocation function (with first-fit algorithm by

default).

quoted

    * Can not be used in NMI handler on architectures without
    * NMI-safe cmpxchg implementation.
    */
-unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+unsigned long gen_pool_alloc_align(struct gen_pool *pool, size_t size,
+		unsigned long align)
   {
   	struct gen_pool_chunk *chunk;
   	unsigned long addr = 0;
+	unsigned long align_mask;
   	int order = pool->min_alloc_order;
   	int nbits, start_bit = 0, end_bit, remain;

@@ -281,6 +284,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,

size_t size)

quoted

   	if (size == 0)
   		return 0;

+	align_mask = ((align + (1UL << order) - 1) >> order) - 1;
   	nbits = (size + (1UL << order) - 1) >> order;
   	rcu_read_lock();
   	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) { @@
-290,7 +294,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool,

size_t size)

quoted

   		end_bit = chunk_size(chunk) >> order;
   retry:
   		start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
-				pool->data);
+				pool->data, align_mask);
   		if (start_bit >= end_bit)
   			continue;
   		remain = bitmap_set_ll(chunk->bits, start_bit, nbits); @@ -

309,6

quoted

+313,22 @@ retry:
   	rcu_read_unlock();
   	return addr;
   }
+EXPORT_SYMBOL(gen_pool_alloc_align);
+
+/**
+ * gen_pool_alloc - allocate special memory from the pool
+ * @pool: pool to allocate from
+ * @size: number of bytes to allocate from the pool
+ *
+ * Allocate the requested number of bytes from the specified pool.
+ * Uses the pool allocation function (with first-fit algorithm by

default).

quoted

+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
+ */
+unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size) {
+	return gen_pool_alloc_align(pool, size, 1);

Passing 1 here would change the behavior of the existing algorithms which
were passing 0 for the align mask

When passing 1 here(align_mask = ((align + (1UL << order) - 1) >> order) - 1), align_mask will be 0.
It will not change the behavior of the existing algorithms.

Yes, you are right, I did the math wrong when looking at the align function.

Laura